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measuring time and distance

Discussion in 'General Electronics Discussion' started by Flatire, Mar 16, 2020.

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  1. Flatire

    Flatire

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    Mar 16, 2020
    just noticed i should have posted in question forum....

    I want to make a device to measure and compare time and distance for my 1/4 mile race car.

    the way i'd like it to work is, record first 1/4mile run and store it. then on my next run,
    in real time compare it to the stored run, having LEDs indicating if the current run is
    faster or slower than the stored run.

    I assume i'll use a pick up on the driveshaft or wheel.

    Thanks for your time and input.
    Tim
     
  2. Bluejets

    Bluejets

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    860
    Oct 5, 2014
    You already have the distance @1/4 mile.

    2 Microcontrollers (preferably)...Arduino of any type would cover the requirement.
    Pickup sensor at the start to detect green light on-time, ideally hard wired.
    Pickup sensor at the 1/4 mile mark to detect when crossing the line and shut down the timer (could be PIR sensor)
    Batteries /power units both ends to operate the devices.
    Wireless Tx and Rx units ...long range NRF24 units should suffice.
    Some kind of display to readout the results .
    16x2 LCD on I2c probably the easiest.(only 2 power and a clock and data line)
    Some knowledge of all the above.

    Failing that, perhaps a stopwatch glued to the wheel is the simplest I can imagine.
     
  3. Nanren888

    Nanren888

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    Nov 8, 2015
    Am I reading this right? You want real-time progress this run compared to the same distance from the prvious or reference run?
    Like a bar display showing running behind, or ahead of previous?

    So what's the quantity of interest? Distance versus time?
    I guess your wheels spin? So distance might be a little tricky to determine accurately.
     
  4. Bluejets

    Bluejets

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    860
    Oct 5, 2014
    Line on the ground don't move no matter how many horses....:)
     
  5. Nanren888

    Nanren888

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    Nov 8, 2015
    So lots of lines to get a real-time readout as he goes?
    Long barcode?
    .
    Hence my question about whether finish time is all he wants, or progress bar comparison as he races towards the end.
     
    Flatire likes this.
  6. Flatire

    Flatire

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    Mar 16, 2020
    yes please..progress bar comparison as he races towards the end.

    Pick up on the front wheel.
    Mercury switch to start the counter
    every 5 rotations 100 max

    stored
    1st run= 5 rotations / 1.122 seconds
    10 rotations / 2.000 seconds
    15 rotations / 2.752 seconds
    20 rotations / 3.456 seconds
    25 rotations / 4.225 seconds
    compare
    2nd run=5 rotations / 1.120 seconds .002 faster
    10 rotations / 1.990 seconds .010 faster
    15 rotations / 2.730seconds .022 faster
    20 rotations / 3.456 seconds .000
    25 rotations / 4.240 seconds .015 slower

    Thanks!
     
    Last edited: Mar 16, 2020
  7. AnalogKid

    AnalogKid

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    661
    Jun 10, 2015
    Taking samples based on wheel rotation means the samples are taken at fixed distances along the track. Normally a system like this would collect data at fixed time intervals, but your way will produce similar results.

    Either way (fixed time interval or fixed distance), there will be an ambiguity at the start of up to 1 wheel rotation. Is this acceptable?

    ak
     
  8. Harald Kapp

    Harald Kapp Moderator Moderator

    10,079
    2,153
    Nov 17, 2011
    Use a laser distance sensor placed at the finish line, aimed at your car.
    Probably a tad expensive plus you'll have to ensure nobody looks into the laser beam.Just joking.

    Use multiple sensors on the wheel to increase accuracy and reduce this ambiguity.
     
  9. Flatire

    Flatire

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    Mar 16, 2020
    That being said, i'd probably take rotation samples from the drive shaft in 4 places each rotation.
    Fixed time intervals if fine.
    Ambiguity at start of 1 driveshaft rotation is acceptable.
    Thanks!
     
  10. Nanren888

    Nanren888

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    Nov 8, 2015
    It seems you have a lot of it sorted out. Which parts are giving you trouble?
     
  11. Flatire

    Flatire

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    Mar 16, 2020
    I'm a long time BMW auto mechanic.
    i don't know how to build electronic things.

    I need a schematic and parts list.
    I know very little about IC's

    Thanks
     
  12. Flatire

    Flatire

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    Mar 16, 2020
    Screen Shot 2020-03-16 at 9.44.59 AM.png
     
  13. Nanren888

    Nanren888

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    Nov 8, 2015
    Often, nowadays, as you have drawn, the easiest answer is a microcontroller, but this requires software rather than hardware. This is not so difficult, but a different skillset.
    A purely hardware solution might be quite complicated, but microcontrollers tend to be very flexible and with many sensor modules and libraries available they are getting much easier and cheaper to use.
    .So, you need time and to watch the wheel rotation sensor on the front wheels. Also need a way to reset things to tell it that you are ready to start. Some configuration to know how many sensor counts per metre, foot, mile, your unit of choice, and something to fix the scale of the how fast/slow means how many LEDs light.
    Driving a few LEDs is not difficult. Counting pulses is not difficult. Depending on your sensor, you may need to debounce a little to get clean counts. You suggested a mercury switch to sense starting. Also possible.Any familiarity with microcontrollers? Many start with arduinos, accessible, cheap, many libraries, but not the only option.

    Might need to add power supply to the figure. Such circuitry likes to have a well regulated power supply and usually low voltage. Also not usually a challenge.
     
    Last edited: Mar 16, 2020
  14. Flatire

    Flatire

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    Mar 16, 2020
    I wanted to purchase an Arduino but i got lost in all of the options.

    any chance you could make me a list of items to purchase i'd really appreciate it because i'm lost in this world.

    Thanks, tim
     
    Last edited: Mar 16, 2020
  15. Flatire

    Flatire

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    Mar 16, 2020
    i'm starting to understand what the Arduino is via Youtube and how Sketch works.
    Once i get all of my hardware i'll circle back around to this forum.
    Cheers!
     
  16. Nanren888

    Nanren888

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    Nov 8, 2015
    I guess there are two main ways to make the led bar display. Simple LEDs on output pins and smart LEDs.
    Simple hardware using one LED per output pin will use more pins, but is conceptually simpler.
    The arduino IDE comes with examples. One of them is "Blink" which shows how to blink an LED. This can be the basis of controlling as many LEDs as you have pins.

    Neopixels as one variety of smart LED strip. Generally software talks to the end one and tells them what to do, so it is as if you only have to wire one of them up, rather than several. A little more xpensive than individual LEDs. Here is a page that talks about using them for various things.
    https://create.arduino.cc/projecthub/robocircuits/neopixel-tutorial-1ccfb9
    .
    Generally many arduino sensors have software libraries to run them, so minimum coding to do.

    Magnetic sensors can be reliable. Here is a page that talks about using a hall-effect sensor on an arduino.
    https://maker.pro/arduino/tutorial/how-to-use-a-hall-effect-sensor-with-arduino
     
  17. Bluejets

    Bluejets

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    Oct 5, 2014
    You're not going to get accurate distance readings from within the moving vehicle without fixed external reference points.
     
  18. Flatire

    Flatire

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    Mar 16, 2020
    This is a time slip from a drag strip.
    R/T is reaction time of the driver.

    E6D10F7C-BF03-4300-B65D-F80709D94EA3.jpeg
     
  19. Nanren888

    Nanren888

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    Nov 8, 2015
    As Bluejets says, it seems that you'll need something extra to get accurate distance measurement. I asked above whether the wheels spin? You suggested monitoring the front wheels. If they slip relative to the ground, you internal counter won't be tracking the true ground, so your onboard idea of distance will be wrong.
    Something that you need to sort out before any of it becomes viable.
     
  20. Flatire

    Flatire

    9
    0
    Mar 16, 2020
    ok, so there will not be any wheel spin!
    IMG_5882.jpg
     
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